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Friday, July 29, 2011

An artist's conception shows how the birdlike dinosaur known as Xiaotingia zhengi might have looked.

By Alan Boyle

The
newfound fossil of a 155 million-year-old feathered dinosaur has led
scientists to claim that Archaeopteryx, the species long held forth as
the "oldest bird," is no bird at all.
Chinese researchers made the claim in Thursday's issue of the journal Nature, and
an outside expert says the study "is likely to rock the paleontological
community for years to come." Ohio University paleontologist Lawrence
Witmer noted that the latest research, focusing on a fossil species
dubbed Xiaotingia zhengi, comes 150 years after the discovery of
Archaeopteryx, which marked a milestone in the study of the origin of
birds.

"It's fitting that 150 years later, Archaeopteryx is right back at center stage," Witmer told me.
Xiaotingia was found by a collector in China's Liaoning Province, a
hotbed for feathered-dino fossils, and sold to the Shandong Tianyu
Museum of Nature. Paleontologists led by Xing Xu of the Chinese Academy
of Sciences analyzed the fossil's skeletal measurements in detail and
fed them into a computer database with measurements from 89 fossilized
dinosaur and bird species, including Archaeopteryx.
Without
Xiaotingia, the computer analysis put Archaeopteryx on the evolutionary
line leading to modern-day birds. But when Xiaotingia was included,
Archaeopteryx was placed in a group of birdlike dinosaurs known as
deinonychosaurs. The differences had to do with details such as the
shape of the wishbone and the skull's snout.

Archaeopteryx was about the size of a modern-day crow, and Xiaotingia was as big as a chicken.

Xu et al., Nature

The fossil skeleton of Xiaotingia zhengi is splayed out in rock.

"If you just looked at Xiaotingia, you'd say, 'Oh, boy, another little feathered dinosaur from China,'" Thomas Holtz​,
a paleontologist at the University of Maryland at College Park who
reviewed the study for Nature, told me. "In and of itself, it is not a
particularly unusual animal. But the combination of traits, at least in
their analysis, pulls Archaeopteryx over to the deinonychosaur side of
things."
The researchers acknowledged that their reclassification
was "only weakly supported by the available data," but they said this
kind of fuzziness was to be expected when the fossils being analyzed are
close to the common ancestor of now-extinct dinosaurs and modern birds.
"This phenomenon is also seen in some other major transitions,
including the origins of major mammalian groups," they wrote.

Witmer agreed: "We're looking at an origin, and consequently it's going to be messy."
The
150 million-year-old Archaeopteryx fossil, which was discovered in
southern Germany in 1861, was long seen as the oldest evidence of a bird
species because the rocky imprint bore traces of feathers. But over the
past decade or two, many dinosaur fossils have been found with evidence
of feathers — to the extent that some scientists have been able to
figure out how the feathers were colored. As a result, some researchers have argued for years that Archaeopteryx should be reclassified.

In the past, creationists have used Archaeopteryx in their arguments
against evolutionary theory, contending that birds always existed in
their feathered form and did not evolve from dinosaurs. Evolution's
critics may try to spin these latest findings to their advantage as
well, Witmer said.
"It may well be they're going to suggest that
we evolutionists don't know what we're doing," he told me. "In reality,
it's just the opposite. It just shows what evolution is all about. A
prediction of evolutionary theory is that it should be really hard for
us to figure out what's going on in an origin."

Archaeopteryx's dethronement means the title of "oldest bird" could fall to other ancient species, such as Epidexipteryx hui, Jeholornis and Sapeornis,
Witmer said. "They're not exactly household names," he noted. "These
new characters have been known only for 10 years or less."
Archaeopteryx, meanwhile, would be lumped in with Xiaotingia as well as
another feathered-dino species called Anchiornis huxleyi.

The
renewed debate over Archaeopteryx's classification is far from
finished. Holtze said he knew some researchers who were inclined to go
with a completely different classification scheme, which would put the
deinonychosaurs along with Archaeopteryx on the evolutionary line
leading to modern-day birds.
The debate could also require a
rethinking of how birds arose, and how features such as feathers
and flight developed. Holtz said some paleontologists have suggested
that Archaeopteryx was not a particularly good flier, and putting it in
the deinonychosaur category would make more sense on that score. It may
turn out that deinonychosaurs gradually evolved from so-so fliers into
feathered but flightless animals. "They would have been nasty predatory
analogs to ostriches," Holtz said.

Holtz acknowledged that
Archaeopteryx "has been our image of what early birds are like, for the
historical reason that it's been known for 150 years as having all these
feathers." The fact that the fossil was found just two years after
Charles Darwin published "On the Origin of Species"
added to its image as an evolutionary icon. A dramatic change in that
image might come as another scientific shock to folks who are already
being told that there's no such thing as a brontosaur, and that Pluto no longer ranks among the solar system's major planets.

"To which I say, 'Get over it!'" Holtz said. "Science is about
changing ideas based on evidence, not about ignoring evidence to conform
to our comfortable ideas."

ABSTRACT: To jump out of water onto sea ice,
emperor penguins must achieve sufficient underwater speed to overcome
the influence of gravity when they leave the water. The relevant
combination of density and kinematic viscosity of air is much lower than
for water. Injection of air into boundary layers (‘air lubrication’)
has been used by engineers to speed movement of vehicles (ships,
torpedoes) through sea water. Analysis of published and unpublished
underwater film leads us to present a hypothesis that free-ranging
emperor penguins employ air lubrication in achieving high, probably
maximal, underwater speeds (mean ± SD: 5.3 ± 1.01 m s–1),
prior to jumps. Here we show evidence that penguins dive to 15 to 20 m
with air in their plumage and that this compressed air is released as
the birds subsequently ascend whilst maintaining depressed feathers.
Fine bubbles emerge continuously from the entire plumage, forming a
smooth layer over the body and generating bubbly wakes behind the
penguins. In several hours of film of hundreds of penguins, none were
seen to swim rapidly upwards without bubbly wakes. Penguins descend and
swim horizontally at about 2 m s–1; from simple physical
models and calculations presented, we hypothesize that a significant
proportion of the enhanced ascent speed is due to air lubrication
reducing frictional and form drag, that ­buoyancy forces alone cannot
explain the observed speeds, and that cavitation plays no part in
­bubble formation.

Penguins can’t fly. But they can get airborne.
In fact, taking to the air, for even a brief instant, is actually a
vital strategy penguins employ to avoid being eating by predators such
as leopard seals or orcas.
Now scientists have worked out the secret technique that penguins use
to get airborne. It involves wrapping their bodies in a cloak of air
bubbles – and it turns out to be the same technique that engineers use
to speed the movement of ships and torpedoes through water.
Another interesting aspect of the discovery is that it was made by
scientists examining in minute detail footage shot for the programme Blue Planet, a landmark natural history series filmed by the BBC’s own Natural History Unit.

It sounds implausible that penguins might get airborne. These
short, squat birds, which tend to live in the colder parts of the
southern hemisphere, are renowned for their waddling walks and flapping
flippers – which are famously great for swimming, but useless for
flying.
But many species of penguin do take to the air.
Due to their body shape, and poor climbing ability, it is difficult
for penguins to haul themselves ashore, especially onto rocky
shorelines. And it can be almost impossible for a penguin to haul itself
out from the ocean onto sea ice.

Emperor penguins create bubble trails (image: Blue Planet, BBC)

So penguins leap ashore: they swim at speed to the surface, burst
through and briefly get airborne to clear the rocks or ice shelf, and
land on their breast.
Smaller species, such as Adelie penguins, can leap 2-3 metres out of the water, landing unscathed onto broken rock. Bigger species, such as Emperor penguins (the
largest of all), reach heights of 20 – 45 cm, but that is enough for
them to leap out of holes in the ice and clear the ice’s edge.
But one aspect of this leaping behaviour has long puzzled biologists.
As the birds swim toward the surface, they trail a wake of bubbles
behind them. No one knew where these bubbles come from, or why there are
there.
Five years ago, that began to change when a group of biologists met
in a pub in Cork, the Irish Republic, before the start of a scientific
symposium.

Professor Roger Hughes
from Bangor University in Gwynedd recalled how he’d seen a wildlife
film in which penguins trailed bubbles in this way and asked his
colleague Professor John Davenport, of University College Cork, if he knew why they did so.

Adelie penguins leap high (image: photolibrary.com)

Professor Davenport did not, but set off to find out with his PhD student Marc Shorten.
Together they obtained footage from the BBC of its Blue Planet
series, which filmed breaching penguins for its Frozen Seas episode.

(Watch below how Emperor penguins first evade a leopard seal, then
when the coast is clear, they trail a wake of bubbles before leaping
from the water)
The scientists slowed down this footage, analysing the speeds and
angles of emperor penguins exiting the water, developing a basic
biomechanical model of what was going on.
During this analysis, the researchers made some interesting
discoveries. The bubbles of air being trailed by the penguins weren’t
coming out of the birds’ lungs via the beak.
Instead, they were coming from the birds’ feathers.

“We were amazed to find that,” Professor Davenport tells me.
The researchers also realised that these air bubbles form a “coat”
around the birds’ bodies as they rocket toward the surface at speeds of
19km an hour.
To investigate further, the three scientists teamed up with Professor
Poul Larsen from the Danish Technical University in Lyngby, who brought
his expertise in mathematics and fluid mechanics to the research.
The four scientists have now just published the results of their study.

The “coat of air bubbles” first noticed on the Blue Planet footage is
indeed what enables the penguins to get air as they leap onto land.
Penguins have great control over their plumage, Professor Davenport tells me.
They raise their feathers to fill their plumage with air, then dive
underwater. As the birds descend, the water pressure increases,
decreasing the volume of the trapped air. At a depth of 15-20 metres,
for example, the air volume has shrunk by up to 75%.

The birds now depress their feathers, locking them around the new, reduced air volume.
The penguin then swims vertically up as fast as it can, and the air in the plumage expands and pours through the feathers.
“Because the feathers are very complex, the pores through which the
air emerges are very small so the bubbles are initially tiny. They coat
the outer feather surface.”
Crucially, this coat of small air bubbles acts as a lubricant,
drastically reducing drag, enabling the penguins to reach lift-off
speeds.

This air insulation effect is known to boat architects and engineers.
By placing a layer of air around a ship’s hull, or torpedo, for
example, designers can dramatically reduce drag, and speed up the boat
or weapon’s passage through the water as a result.
But “this process has never been thought of before as having a biological role,” says Professor Davenport.
The penguins also appear to have overcome one other issue that
blights naval architects trying to exploit “air lubrication” underwater.

The moment before lift off (image: Blue Planet, BBC)

Although a coat of tiny bubbles dramatically reduces drag, it can
also have a major slowing effect if the bubbles reach a ship or
torpedo’s propeller. That’s because the propeller starts pushing against
air not water.
However, a penguin’s flippers, its means of propulsion equivalent to
the propeller, are held outside of the bubble clouds, so they are not
affected.

Monday, July 11, 2011

'Empire of Ice': The scientific quests of the Antarctic explorers

In "Empire of Ice," Pulitzer Prize-winning
author and historian Edward J. Larson looks at how dedication to science
powered many of the Antarctic's most daring expeditions.

By David B. Williams

Special to The Seattle Times

'An Empire of Ice: Scott, Shackleton, and the Heroic Age of Antarctic Science'
by Edward J. Larson
Yale University Press, 326 pp., $28

Leaving in the pitch black of the Antarctic winter of 1911, Edward
Wilson, Apsley Cherry-Garrard and Birdie Bowers set out to find
penguins. They were part of Robert Falcon Scott's second Antarctic
expedition. To reach the birds, they man-hauled two sledges carrying 750
pounds, which often led to them having to relay the overweight sledges,
so that for each mile advanced, they walked three. Moonlight provided a
little light, but still they dropped into unseen crevasses and bumped
into ice hummocks. And it was rather chilly, with temperatures dropping
to minus-75.8 degrees F.

When they arrived at the penguin colony, the men built a stone hut,
covered by a canvas tent. They were able to collect a few birds and eggs
before a blizzard hit. Trapped for days, Cherry-Garrard wrote that the
wind "sounded like the rush of an express train through a tunnel."
Everything was frozen, and when the wind took the tent, the men had to
cower in their exposed bags.

Their return trip to their base was even worse. Having had little
success at the penguin colony, they had to man-haul 16 hours a day in
mostly darkness, and Cherry-Garrard's jaw chattered so violently he
shattered all of his teeth.

This "worst journey in the world," as it came to be called, was not
the only time Wilson had risked his life to observe Antarctic penguins.
He had studied the birds on Scott's previous expedition. But all of the
hardships were worth it because "they did it for science," writes Edward
J. Larson, in his new book, "An Empire of Ice: Scott, Shackleton, and
the Heroic Age of Antarctic Science."

Writing about Scott's and Ernest Shackleton's Antarctic expeditions
is a cottage industry. New books analyzing everything from the men's
leadership abilities to how and why their reputations have changed
appear regularly.
To his credit, Pulitzer Prize-winner Larson offers a new take by
looking at how science drove many of the expeditions. As he did in
previous books such as "Summer for the Gods" and "Evolution's Workshop,"
Larson combines careful reading of the primary documents, a thorough
knowledge of the players, and first-rate writing to produce a compelling
book. That having been said, this book's main appeal will be to those
already familiar with the expeditions and those interested in the
history of science.

My only complaint is the maps. I appreciate that Larson used historic
maps from the expeditions, but they are very hard to read and often
filled with too much surplus data. The photographs, however, are a nice
addition.
The men took their research seriously, often making incredible
sacrifices in the name of science, whether it be meteorology, biology or
geology. They did so in part because they were British and felt that as
citizens of the leading nation of the world, it was their
responsibility to be the first to penetrate the unknown realms, to study
them, and to write lengthy descriptions of what had been found.

Larson effectively argues that although some may look derisively back
at Scott and Shackleton as relics of the Edwardian age, their
scientific work should be considered as "modern and forward-looking
enterprises." After all, Antarctica has become "fundamentally a place of
science," and these expeditions led the way.

Friday, July 8, 2011

New research finds that pterosaurs, flying reptiles from the time of
the dinosaurs, were not driven to extinction by the birds, but in fact
they continued to diversify and innovate for millions of years
afterward. (Credit: iStockphoto/Linda Bucklin)

The Rise and Rise of the Flying Reptiles: Pterosaurs Not Driven Into Extinction by Birds, Study Reveals

ScienceDaily (July 7, 2011) —
Pterosaurs, flying reptiles from the time of the dinosaurs, were not
driven to extinction by the birds, but in fact they continued to
diversify and innovate for millions of years afterwards.

A new study by Katy Prentice, done as part of her undergraduate
degree (MSci in Palaeontology and Evolution) at the University of
Bristol, shows that the pterosaurs evolved in a most unusual way,
becoming more and more specialised through their 160 million years on
Earth. The work is published in the Journal of Systematic Palaeontology.

"Usually, when a new group of animals or plants evolves, they quickly
try out all the options. When we did this study, we thought pterosaurs
would be the same," said Katy. "Pterosaurs were the first flying animals
-- they appeared on Earth 50 million years before Archaeopteryx, the
first bird -- and they were good at what they did. But the amazing thing
is that they didn't really begin to evolve until after the birds had
appeared."
Katy's study was done in conjunction with her supervisors, Dr
Marcello Ruta and Professor Michael Benton. They looked at 50 different
pterosaurs that ranged in size from a blackbird to the largest of all,
Quetzalcoatlus, with a wingspan of 12 metres, four times the size of the
largest flying bird today, the albatross. They tracked how all the
pterosaur groups came and went through their history and recorded in
detail their body shapes and adaptations.

The new work shows that pterosaurs remained conservative for 70
million years, and then started to experiment with all kinds of new
modes of life. After birds emerged and became successful, the pterosaurs
were not pushed to extinction, as had been suggested. It seems they
responded to the new flyers by becoming larger and trying out new
lifestyles. Many of the new lifestyle adaptations were seen in the
pterosaurs skulls, as they adapted to feed on different food sources;
some were seed-eaters, many ate fish, and later ones even lost their
teeth. The rest of the body also showed a surprising amount of variation
between different groups, when considering that the body forms have to
retain many features to allow flight.

"Pterosaurs were at the height of their success about 125 million
years ago, just as the birds became really diverse too," said Dr
Marcello Ruta. "Our new numerical studies of all their physical features
show they became three times as diverse in adaptations in the Early
Cretaceous than they had been in the Jurassic, before Archaeopteryx and
the birds appeared."

Pterosaurs dwindled and disappeared 65 million years during the mass
extinction that killed the dinosaurs. In their day they had been a fair
match for the birds, and the two groups divided up aerial ecospace
between them, so avoiding conflict.

"We're delighted to see a student mastering some tough mathematical
techniques, and coming up with such a clear-cut result," said Professor
Michael Benton. "Palaeontologists have often speculated about the coming
and going of different groups of animals through time, but the new
study provides a set of objective measurements of the relative success
and breadth of adaptation of pterosaurs through their long time on the
Earth."
Further information can be found on the Palaeobiology and
Biodiversity Research Group's website: The rise and rise of the flying
reptiles (http://palaeo.gly.bris.ac.uk/macro/pterosaurs.html).

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Bristol.

University of Bristol (2011, July 7). The
rise and rise of the flying reptiles: Pterosaurs not driven into
extinction by birds, study reveals. ScienceDaily. Retrieved July 8, 2011, from http://www.sciencedaily.com­/releases/2011/07/110706101608.htm

ScienceDaily (July 2, 2011) —
A developmental biologist at New York Medical College is proposing a
new theory of the origin of birds, which traditionally has been thought
to be driven by the evolution of flight. Instead, Stuart A. Newman,
Ph.D., credits the emergence of enlarged skeletal muscles as the basis
for their upright two-leggedness, which led to the opportunity for other
adaptive changes like flying or swimming. And it is all based on the
loss of a gene that is critical to the ability of other warm-blooded
animals to generate heat for survival.

Dr. Newman, a professor of cell biology and anatomy, studies the
diversity of life and how it got that way. His research has always
centered on bird development, though this current study, "Thermogenesis,
muscle hyperplasia, and the origin of birds," also draws from
paleontology, genetics, and the physiology of fat.
Dr. Newman draws on earlier work from his laboratory that provided
evidence for the loss, in the common dinosaur ancestors of birds and
lizards, of the gene for uncoupling protein-1 (UCP1). The product of
this gene is essential for the ability of "brown fat," tissue that
protects newborns of mammals from hypothermia, to generate heat. In
birds, heat generation is mainly a function of skeletal muscles.

"Unlike the scenario in which the evolution of flight is the driving
force for the origin of birds, the muscle expansion theory does not
require functionally operative intermediates in the transition to
flight, swimming, or winglessness, nor does it require that all modern
flightless birds, such as ostriches and penguins, had flying ancestors.
It does suggest that the extinction of non-avian dinosaurs may have been
related to a failure to evolve compensatory heat-generating mechanisms
in face of the loss of UCP1," says the scientist

New York Medical College (2011, July 2). New theory on origin of birds: Enlarged skeletal muscles. ScienceDaily. Retrieved July 3, 2011, from http://www.sciencedaily.com­/releases/2011/06/110622115317.htm